Usual Suspects, The Easter Egg - Christopher McQuarrie

In the scene where each of the suspects is being interrogated individually, we see the torsos of two cops who are circling them as the ask questions. The cop with the somewhat raspy voice, and whose face is partially shown as Gabriel Byrne is interrogated, is none other than Christopher McQuarrie - the writer of the screenplay for The Usual Suspects. He actually pops up in a few other scenes throughout the movie, including:
the line-up scene - in which he is the cop sitting on the left side looking out at the suspects.
and
the final scene - when agent Kujan has just realized that he's been suckered in, and runs outside to find Verbal but just misses him, there is a uniformed cop in the background who is played by McQuarrie.